Patch

diff --git a/Documentation/block/biovecs.txt b/Documentation/block/biovecs.txtindex 25689584e6e0..bb008f7afb05 100644--- a/Documentation/block/biovecs.txt+++ b/Documentation/block/biovecs.txt@@ -117,3 +117,27 @@ Other implications:
size limitations and the limitations of the underlying devices. Thus
there's no need to define ->merge_bvec_fn() callbacks for individual block
drivers.
++Usage of helpers:+=================++* The following helpers whose names have the suffix of "_all" can only be used+on non-BIO_CLONED bio. They are usually used by filesystem code. Drivers+shouldn't use them because the bio may have been split before it reached the+driver.++ bio_for_each_segment_all()+ bio_first_bvec_all()+ bio_first_page_all()+ bio_last_bvec_all()++* The following helpers iterate over single-page bvecs. The passed 'struct+bio_vec' will contain a single-page IO vector during the iteration++ bio_for_each_segment()+ bio_for_each_segment_all()++* The following helpers iterate over single-page bvecs. The passed 'struct+bio_vec' will contain a single-page IO vector during the iteration++ bio_for_each_bvec()